Before the invention of clocks people used devices such as sundials, sandclock etc to know the time. Wikipedia gives you the measurements once used by south Indians (time,area, weight). My doubt is what is the ancient thamizh people used to know time. Are there any references stating they used devices to know time.
The Tamul and Telugu both used the same system of time keeping, which was derived from ancient Hindi methods and was based on a 60-hour day, the word "ghurry" meaning an hour (24-minute period):
The standard method of time keeping was the water clock which was used by the Hindus and other peoples of India for thousands of years going back. The water clock was known as the "ghurry al" and was typically made of copper, brass or gold. The ancient Hindu water clock is known explicitly from a detailed description by Lalla, the famous 8th century Indian astronomer (qv).